As part of the disease process, a number of pathogenic bacteria deliver toxins to their host cells. Some of bacteria have evolved a structure referred to as a Type 3 Secretion System (T3SS). The T3SS is essentially a needle that the bacterium uses to penetrate the host cell. The bacterium then injects the toxins through the T3SS needle into the host cell.
We have previously described engineered non-pathogenic cells that use this system for delivering some kinds of payloads into cells (see, e.g. WO/2014/138324).